I thought I already had the time up there in the top bar, and it may have been so in previous Ubuntu versions (don't remember, my Ubuntu laptop is just one of three computers I use). Only that I just noticed - me being someone who never wears a watch, has the cellphone turned off 95% of the time and relying on the computer to tell the time - that there is no time being displayed anywhere, and I had expected it in the top bar on the Unity desktop.

I searched around but found no obvious solution, but I'm sure someone immediately knows how I can get my time (back?) into the top bar?

I'm not aware I changed something. I definitely didn't deliberately do so. No, no date either. There is no time&date in the "system settings" window...(?)
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SomeoneFeb 10 '12 at 10:36

2

Case closed - I had removed everything using "evolution", and teh indicator applet was one of those packages. Why on earth it needs evolultion(-data-server) is another question (I understand - calendar data; but didn't they switch to Thunderbird). I declare your answer a "solution" because it helped me find the problem.
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SomeoneFeb 10 '12 at 10:39

I had the same problem. Just to add specifically, installing indicator-datetime is what fixed it.
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DisgruntledGoatMay 8 '12 at 23:50